1. Field of the Invention
The present invention relates to the structure of an electronic device such as personal computers and word processors, and more specifically, to a liquid crystal display (LCD) device equipped with the electronic device and a method of manufacturing a reflection layer in the liquid crystal display device. The present invention may also be applied to an electro-optical device having the liquid crystal display device.
A “semiconductor device” as used herein refers to a general device activated by a semiconductor. Therefore, the above-noted liquid crystal display device and the electro-optical device also fall within a category of semiconductor device. For clarification, the terms of “liquid crystal display device” and “electro-optical device” are separately used herein.
2. Description of the Related Arts
Typically, a reflection type liquid crystal display device is known. The reflection type liquid crystal display device is more advantageous than a transmission type liquid crystal display device in that a lower power consumption may be achieved since no back light is used. Incidentally, the reflection type liquid crystal display device has been increasingly required for a direct-vision type display for mobile computers and video cameras.
FIG. 20 is a schematic view showing an example of a conventional structure. Referring to FIG. 20, between a substrate 10 and an opposing substrate 17 are provided switching elements 11 such as thin film transistors, an interlayer insulating film 12, pixel electrodes 13, an orientated layer 14, a liquid crystal layer 15, the orientated layer 14, and an opposite electrode 16 in the stated order from the top surface of the substrate 10. Incident light 20 is reflected by the pixel electrodes 13 to generate a reflection light 21. It is to be noted that although all components are not shown in FIG. 20, which is a schematic view, a number of switching elements and a number of pixel electrodes are formed in a matrix on the surface of the substrate 10.
The reflection type liquid crystal display device utilizes an optical modulating action of the liquid crystal to select the state where the incident light is reflected by the pixel electrodes to be outputted to the outside of the device and the state where the incident light is not outputted to the outside of the device, thereby allowing for the light or dark indication, and a combination thereof would allow an image to be displayed. Each pixel electrode is made of a metal with high reflectivity such as aluminum, and is electrically connected to a switching element such as a thin film transistor.
FIG. 21 is a top view showing a conventional liquid crystal panel (corresponding to that shown in FIG. 20), and is a magnification showing a portion of a display region 22. In FIG. 21, the switching elements 11, the display region 22 consisting of the pixel electrodes 13, etc, a driver circuit 23 for driving in an X-direction, and a driver circuit 24 for driving in a Y-direction are provided on the substrate 10.
In such a conventional arrangement in which the pixel electrodes made of a metal material having a high reflectivity are used as a reflection layer, the light reflectivity is conventionally limited (e.g., less than 92% for an aluminum electrode).
Further, as shown in FIG. 21, there is a fear that light is leaked from a gap formed between the pixel electrodes 13 that are separately arranged from each other for every pixel. Therefore, a problem of a so-called light leak phenomenon occurred in which a reduced off resistance of the switching elements 11, occurrence of a photo carrier, and the like causes charges of the pixel electrodes to leak, thereby reducing a liquid crystal driving voltage.
Since the conventional reflection layer (pixel electrodes made of a metal material) does not provide a sufficient reflection and irregular reflection of light, there is a problem with a brightness suitable for a liquid crystal display device (in particular, a direct-vision-type reflection type liquid crystal panel). Also, in the conventional reflection layers (pixel electrodes), gaps between adjacent reflection layers (pixel electrodes) are large, thereby causing the light leak.
Further, conventionally, such a problem has been arisen in which the reflectivity of the refection layer is lowered due to formation of an orientated layer with a high refractive index on the reflection layer (electrodes made of a metal material). For example, in the case where an orientated layer (having the refractive index of 1.6) is formed on a deposited aluminum film (having the reflectivity of 91.6%), the reflectivity is lowered to 87.4% in calculation, or is lowered to approximately 85-86% according to an actual experiment. Alternatively, when silver is used as a metal material, a silver electrode having the reflectivity as high as 97.6% is liable to be oxidized. Thus, the silver is difficult to be employed because of being difficult to be processed.